1. Field of the Invention
The present invention relates to a photoelectric conversion device, and more particularly to a photoelectric conversion device equipped for example with a one-dimensional line sensor for reading image information of an original document maintained in contact therewith and moved relative thereto, and adapted for use in facsimile apparatus, image reader, digital copying machine, electronic blackboard or the like.
2. Related Background Art
FIG. 1 is a cross-sectional view, along the sub scanning direction, of a conventional contact photoelectric conversion device utilizing a linear sensor.
FIG. 2 illustrates common lines of the matrix wiring in the conventional photoelectric conversion device shown in FIG. 1, and capacitances between the lines.
A light shielding layer 2 having an aperture for illumination 3 and individual electrodes 4 of matrix are formed on a translucent insulating substrate 1, and a translucent insulating layer 5 is formed for insulating photoelectric conversion elements 6 from the light shielding layer 2. On said layer there are formed photoelectric conversion layers 16, for example of amorphous silicon (a-Si), of photoelectric conversion elements 6 arranged by a number of N.times.M in the main scanning direction. The photoelectric conversion elements 6 are respectively connected to common lines 7 of a number M of a matrix wiring, through contact holes 17, 18. A thin glass plate such as microsheet glass may be adhered thereon as a transparent protective layer 8, and a hard thin film for example of Al.sub.2 O.sub.3, SiC or Si.sub.3 N.sub.4 may be formed on the transparent protective layer 8. The light entering from the aperture 8 is reflected by the original 10 advanced by a roller 9, and the intensity of the reflected light is converted into electrical signals by the photoelectric conversion elements 6.
However such contact photoelectric conversion device has been associated with a drawback of generating noises in the signal output circuit due to the electrostatic charge generated by the friction between the original document and the transparent protective layer composed of thin glass plate or the hard insulating film formed thereon, which are both highly insulating.
In particular, as shown in FIG. 2, the common lines of matrix wiring run over the entire length of the photoelectric conversion device in the main scanning direction and are easily subject to the influence of electrostatic charges. Among the parallel common lines, as shown in FIG. 2, outer ones show less capacitive coupling with other lines than inner ones, and are more easily influenced by external noises such as electrostatic charges. FIG. 2 illustrates only the capacitances with two closest lines on either side. A line M2 has capacitative coupling with four lines M, M1, M3 and M4, but the line M has coupling with only two lines M1 and M2. Consequently, as shown in FIG. 3(b), the signals of outer lines tend to receive stronger influences.